The present invention relates generally to communications systems and, more particularly, to method and apparatus for bit-level PDSCH (Physical Downlink Shared Channel) muting and/or receiver puncturing in LTE-A (Long Term Evolution-Advanced) heterogeneous networks.
The next-generation cellular system, i.e., the LTE-A network, is being designed to improve the spectral efficiency per unit area by reducing the cell size via heterogeneous deployment of a diverse set of base stations (BSs). In a heterogeneous cellular network, the macro BSs are deployed in regular and planned manner with high transmit power (the typical value is 46 dBm) and the overlaid pico BSs are deployed in the poor coverage area (e.g., the edge of a macro cell) with relatively low transmit power (the typical value is 30 dBm). Such an overlaid BS deployment can improve the coverage and provide capacity gain by increasing spatial reuse of the spectrum.
Consider the downlink of a LTE-A heterogeneous network. The pico user terminals or UEs (i.e., the UEs that are associated to pico cells) suffer strong interference from its neighboring macro BSs due to the high transmit power of the macro BSs. In order to improve the throughput performance of the pico UEs, especially those on the cell edge, intelligent inter cell interference coordination (ICIC) is needed to deal with the interference between macro BSs and pico UEs. In LTE-A Rel-10 ICIC, the macro BSs can mute certain subframes, which are called almost blank subframes (ABSs), in order reduce the interference to the pico UEs. In an ABS, most resource elements (REs) are blank and only a small amount of REs carry some system information (e.g., the cell-specific reference signals (RSs) and synchronization signals). As such, the pico UEs can achieve higher data rate when the macro BSs transmit ABSs due to the reduced interference level.